As a cinematic effort, “Atlas Shrugged: Part I” is competent; in service to Ayn Rand”s epic novel, it”s less so.

For decades, “Atlas Shrugged” has been considered unfilmable, too long for one movie and too didactic for mass appeal. The version that finally emerged based on the book”s first 10 chapters doesn”t do much to alter those perceptions.

Gaps of characterization and narrative are expected when condensing hundreds of pages into less than 100 minutes. When the prose being pared is as dense as Rand”s, the casualties of abridgement are multiplied.

It”s difficult to imagine devotees of the book to be satisfied with what director Paul Johansson and screenwriters John Aglialoro and Brian Patrick O”Toole have done with it.

It may be a different story for the tea party movement gleaning inspiration from Rand”s 1957 novel, which “Atlas Shrugged: Part I” exclusively targeted with a viral marketing campaign.

The script hits all the right rhetoric about overreaching government and stunted liberties to make them happy, and who has time between rallies to read an 1,148-page novel, anyway?

But there”s enough in “Atlas Shrugged: Part I” to make parts II and III (if they”re produced) seem like less of a chore. Not the least of which is Taylor Schilling”s steely portrayal of Dagny Taggart, the driven railroad tycoon at center stage.

Dagny”s railway is the nation”s largest, in a not-too-distant future when gasoline costs $34.50 per gallon, the Dow is under 4,000 points and a Department of Redistribution is spreading the wealth.

Rail is the cheapest method of moving people and products, but Dagny”s piece of the industry is rocked by a derailment in Colorado, one result of a crumbling infrastructure.

By the way, the screenplay has all this happening in 2016; it isn”t a stretch to guess whose presidency is tacitly responsible for the mess.

Dagny plans to rebuild the railway using a lighter and stronger alloy invented by Henry Reardon (moving mannequin Grant Bowler).

They face opposition from lobbyists with vested interests in what smacks of socialism, and union demands.

Dagny and Henry fall in love and, in an undeveloped tangent, discover an engine that can turn air into static electricity. Just one more ingenious idea for society”s lower-income parasites to exploit.

Meanwhile, the world”s greatest thinkers and doers are disappearing. They”ve been convinced by the mysterious John Galt (Johansson in shadows) to go “on strike,” withholding their talents from a culture that won”t show appreciation by allowing them to keep all their profits.

“Atlas Shrugged: Part I” doesn”t end as much as stop dead in its tracks, with a cliffhanger involving an oil refinery disaster and yet another missing industrialist. All the shop talk about copper mines, steel mills and railroads seems superfluous by then.

I”m confident that the threads come together in Rand”s subsequent chapters but at this film”s conclusion, the chances of seeing parts II and III in theaters seem slim.GO!